Cosmonauts on board the International Space Station (ISS) conducted a spacewalk in order to fix a leaking radiator on Wednesday. 

The leak, confirmed earlier this month by Russian space agency Roscosmos, came from the backup radiator mounted on the outside of the Nauka module launched in 2021. The main radiator remains operational, but Rosmocos scheduled in a spacewalk to fix the problem. 

Inspecting the source of the leak, Oleg Kononenko reported seeing a number of holes on the radiator panel.

"The holes have very even edges, like they've been drilled through," Kononenko told Moscow Mission Control, Space.com reports. "There are lots of them. They are spread in a chaotic manner."

The cosmonauts were equipped with a cloth towel to soak up any escaping liquid, but Kononenko was told to leave the area immediately after encountering a blob of coolant, which had moved onto his safety tether.

After fellow cosmonauts partially fitted a small radar antenna to the outside of the module, and launched a nano-satellite that sadly failed to deploy its sail, Kononenko headed inside, placing the tether in a secure bag in case of contamination.

The radiator, which has been isolated from supply lines, will be fixed in a future space walk. It remains unclear what the cause of the leak was in the first place.